Field of the Invention
The present invention relates to a sheet processing apparatus configured to perform predetermined processing on, for example, a sheet conveyed from an image forming apparatus, and to an image forming system including the sheet processing apparatus.
Description of the Related Art
Hitherto, there has been provided an image forming system in which a sheet processing apparatus is connected to an image forming apparatus such as a copying machine, a printer, a facsimile, and a multifunction peripheral of those. The sheet processing apparatus is configured to perform various types of post-processing such as sorting processing, aligning processing, offset processing, binding processing, folding processing, and perforating processing on sheets discharged from an image forming apparatus. The sheet processing apparatus is configured to place sheets from the image forming apparatus onto a processing tray, perform necessary post-processing, and then convey the sheets onto a stack tray.
In general, the sheet processing apparatus aligns a plurality of sheets to form a bundle of sheets and then performs post-processing, e.g., binding processing. At this time, when time for processing the bundle of sheets is longer than a conveyance time interval of sheets, there arises a disadvantage that a first sheet of a next bundle of sheets cannot be received during the processing on the preceding bundle of sheets. Therefore, there has been proposed a sheet conveyance device configured to adjust a conveyance speed of a sheet between an image forming apparatus and a sheet processing apparatus to increase an interval between bundles of sheets and obtain time for processing a bundle of sheets (see, for example, Japanese Patent Application Laid-Open No. 2009-120333).
Moreover, there has been known a sheet processing apparatus including a buffer portion, which is arranged on upstream of a sheet conveyance path and configured to convey a plurality of overlaid sheets, to feed the plurality of overlaid sheets as a bundle of sheets to downstream (see, for example, Japanese Patent Application Laid-Open No. 2004-277094). According to the sheet processing apparatus of Japanese Patent Application Laid-Open No. 2004-277094, the plurality of sheets overlaid in the buffer portion are fed with a predetermined time delay. With this, necessary time for processing to be performed on a preceding bundle of sheets is secured.